Oh boy...it's been so long I've forgotten about this. The final evolutions are currently catchable on a single map in the game (or evolvable through trade). From looking at their indicated areas in the Pokédex, these are where they are:

Note that the rarity of these Pokémon is high, so you'll need to search a bit. That, or just fast-forward in your emulator! Otherwise, they're still evolvable through trade.

I didn't want to break canon with the official Pokémon games, so they all still evolve the same way. I always intended to add a method that simulated the post-trading process into the game, but I'm pretty sure I don't have the know-how to do that right now.

I encountered some of those Johto ones, but I never made the connection that that's what the first post was referring too. lol I thought it meant there was a new area somewhere just with the trade evolutions. Good to know. Thanks.